This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. The intravital microscopy system represents a sophisticated tool to dissect complex physiological or pathological cell-cell or cell-matrix interactions such as leukocyte recruitment in inflammation and atherosclerosis, lymphocyte homing in immune development, and stem cell homing in hematopoiesis. Our core facility is equipped with an advanced Nikon ECLIPSE E600-FN intravital epifluorescence microscope with water immersion objectives connected to a Dage-MTI DC-330 3CCD color camera, a SVHS video cassette recorder, and a Microvessel Velocity OD-RT Doppler apparatus. The system also has a Nikon SMZ800 stero microscope for surgical preparation, and an advanced Dell computer for data acquisition and analysis. Using the system, we are able to directly quantify adhesive interactions of circulating leukocytes with vascular endothelium in several ways (i.e., rolling velocity, rolling flux, number of adherent leukocytes in a defined area).